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Oct 1, 2008

AC mains limiter

Hi,

In Japan the capability of a single house-hold type AC mains outlet is 15A at 100V. So I think the circuit breaker may work when a PowerMathch drives 1/3 of maximum power (1320 output / 1726 AC mains) in certain situation. Besides, there is a case also in other countries that several PowerMatches are used with single outlet and there is a possibility the AC mains breaker will work in this case, too. Is there a way to avoid running breaker? Or do you plan to add an AC mains limiter to PowerMatch that can be set up with Designer?

KI
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Sep 12, 2008

Re: AC mains limiter

Hi KI,

The PowerMatch amplifier is designed to work over a wide range of line voltages down to 100V. At 120V, it can run at sustained 1/3 power on all channels simultaneously. It will not achieve that sustained power on all channels with a 100V line voltage. This is not a problem unless your source material is high amplitude sine waves. The PowerMatch amplifier is prevented from delivering more power than the AC lines can supply by an algorithm that monitors the line current and reduces audio level to prevent the circuit breaker from tripping. With high amplitude signals, the short term line current draw can allow maximum rated power on all outputs, but it will settle down to about 15.5A. Your 15A breaker may be too low to prevent tripping with high level test signals running into loads, especially if there are multiple PowerMatch amplifiers on one breaker. If you really want to max out the power, I recommend using a 20A circuit for each PowerMatch. Better yet, for an installation use a 200V or higher mains supply if it is available. With >200V, the breaker and breaker protection algorithm will not be a factor.

On the other hand, with real audio for source material and the amplifier pushing the limits, you will rarely see the line current draw exceed ~3A. The household breakers should be able to sustain brief current spikes exceeding 15A.

Regards,
Chris
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Re: AC mains limiter

Hi Chris,

Thank you for reply. I understand that it is better 20A circuit is provided for each PM8500s. And I read up on Japanese circuit breaker. One of the specification data of circuit breaker says the tripping time at 300% of prearranged current is approximately between 2.0s to 20.0s. I was explained PM8500 can deliver 4000W in total for 1.0s with 120V AC and 45 amps are drawn for 1.0s from an outlet at this time. So it means if a breaker for 15A circuit is used maximum power 4000W for 1.0s can thru this breaker, right?

I talked about AC mains with a consultant who is our pyramid partner and he said it is better that we provide optional cable which have a connector for 30A current called “C-type” in Japan (attached photo). Though typical Japanese theaters or halls equip this type outlet have you seen it?

By the way, the attached AC cable of PM8500 is written as “15A 125V”(attached photo). Is this cable only for the prototype or the same for the product? The consultant also said this cable is just fine so we should chose a little more thick one. As far as I inspected a cable which has 2.0 square millimeters of a cross section can be used for 20A of current but under high temperature situation such as the case that several cables are gathered in one place thicker cable should be used. What do you think about it?

Best regards,
KI
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Re: AC mains limiter

Hi Kakudo -

You wrote:

So it means if a breaker for 15A circuit is used maximum power 4000W for 1.0s can thru this breaker, right?

Answer: Yes, that is correct.


btw, referencing your first post, we do not recommend that:

several PowerMatches are used with single outlet .

They require a single outlet of at least 15A per PM8500.


You also asked about a 30A adapter: That may be a good idea, to make it more convenient to connect to that style of outlet. However, from a power supply point of view, Gonzo will only draw a long-term average of 15 A, and so the 30 A circuit is not required.

It is true that the larger wiring in the 30A circuit may keep the voltage at the outlet more steady with high current peaks. This depends on the circuit wiring lengths between the outlet and the breaker panel as well as other factors.

The power cable supplied is the final cable and our thought is that it is quite adequate for the job, and it of course meets all safety requirements.

Since the cables are rated for average power, not peak, and Gonzo never draws more than 15A average, it is within the specifications of the cable.

I hope that helps!

Best Regards,
Bill
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Jun 26, 2011

Re: AC mains limiter

Hi Bill,
I have a question about the PM8500. Its mains circuit is 120V/20A (USA), so the input power is 2400W, and with the efficiency of 75%, how come the rated output power is 4000W?

Thank you!
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Re: AC mains limiter

Hi Sunny.

The PM8500 will sustain full power within 1 dB for 1 second with a 120V/20A mains circuit. During the 1 second the PM8500 will draw more than the rated current from the mains circuit. After this 1 second, a protection algorithm will reduce the signal level to prevent tripping breakers. The PM8500 will not draw more than 15A long term average current. The PM8500 can easily deliver sustained 1/3 rated power on a 120V/20A circuit and can provide full power for short term peak demands.

Best regards,
Chris
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Re: AC mains limiter

Hi Chris,
Thank you for your response.
So the 4000Watts is the Peak power rather than rated power of PM8500?
And for DXA2120 and FS4400, 120Watts/channel and 400Watts are the rated power or the peak power?
Looking forward to your answer! Thank you!
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Re: AC mains limiter

Hi Sunny,

Thanks for your questions. I'd like to add to Chris' answers, since this gets a little into how amplifiers are rated.

4,000 W is the rated power of the amplifier. That is rated the same way all professional power amplifiers are.
It is an rms (root-mean-square) rating. We and other pro amp manufacturers do not use the misleading "peak" rating which would be twice as high as the rated power. That would refer to the instantaneous power at the peak of the sine wave.


Amplifiers vary in how long they can sustain their rated power. Linear output stage amplifiers can sometimes go longer than switch-mode amplifiers, for various technical reasons. But fundamentally it is a manufacturer's choice.

We have measured multi-channel switching amplifiers that can sustain their rated power for as little as 50 msec, or up to one or two seconds. Those are all highly respected power amplifiers, though some are lower power than the PM8500.

We designed the PM8500 to sustain it's rated power for one second with 120 VAC input, and two seconds with 230 VAC input.

What this gives the system designer is the knowledge that if you need a system rated at 4,000 W, and you specify the PM8500, you will have a solid 4,000 W, and you will never trip a 20 A breaker. And you only had to install one AC line to achieve it.

The specifications you mention for the other products are also the rated power.


Thanks!
bill